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Updated 2:00 PM January 13, 2004
 

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Medicinal chemist dives for new cancer drugs under the sea


Many scientists look for new drugs by synthesizing compounds in their laboratories. David Sherman dives for sea sponges and sediment off the coast, islands and reef systems of Papua New Guinea in the South Pacific.

David Sherman during a dive on a pristine reef in the Bismarck Sea, Papua New Guinea. Sherman collects marine sediments, cyanobacteria and sponges to study the their medicinal, biochemical and microbiological properties for discovery and development of new anti-cancer agents and antibiotics. (Photo courtesy David Sherman)

Though medicine has a long history of making drugs based on naturally occurring materials, such as antibiotic penicillin that comes from mold, Sherman says most of those efforts have focused on dry ground.

"We've barely scratched the surface of what's out there," says Sherman, the John G. Searle Professor of Medicinal Chemistry, College of Pharmacy; a professor of chemistry; and professor of microbiology and immunology, Medical School.

Sherman headed to the Solomon Sea in December with a dozen scientists and about half as many crew members. They went diving two or three times a day. After dinner every night, one of the scientists lectured about his or her specialty. The two-week trek last month was Dec. 8-23.

"This is the fourth field expedition in Papua New Guinea that I have gone on, and this by far was the most successful in terms of rich and diverse habitats," Sherman says. "We were able to collect over 10 times more samples than previous trips and expect to find exciting new drug-like molecules such as cancer-fighting agents and antibiotics."

Sherman chooses dive sites with high biodiversity and collects organisms that show promise as anti-cancer drugs. Sponges, for example, produce a wide array of biologically active materials he's interested in, and he also looks at algae, coral rubble and sediments from shallow- and deep-water environments.

He works with geologists and geophysicists to examine the oceanography and determine how old an area of the ocean is, and with sponge taxonomists to help him keep track of what has been studied elsewhere. After collecting materials, microbiology, genetics and biochemistry help his team understand the possibilities.

Sherman collaborates with the National Cancer Institute and Novartis Oncology for his research and has high hopes for the cancer-fighting potential of the materials he brings up. One of the field's most exciting recent cancer leads was found from a unique actinomycetes bacterium collected near a remote island in the Bismarck Sea.

Sponges and their microbial symbionts, which are found near sponges and which live inter-dependently with sponges, also have been providing many compounds that respond to specific cancer targets, he says. Several currently are in clinical trials.

One limitation continues to be adequate access to source material. Sherman hopes work like his will produce large amounts of a desired compound, limiting the need to return to pristine environments to collect materials.

The natural materials hold such great promise because humans, though capable of remarkable feats, can't begin to generate the amazing, rich complexity of what happens in nature, Sherman says. "Bacteria are fantastic organic chemists. We can spend three years making a compound that bacteria can make in three seconds as a natural part of their metabolism," he says.

Sherman's fascination with how aquatic microorganisms make products that might lead to anticancer compounds began by serendipity—as an undergraduate at University of California at Santa Cruz, he took a scuba class and organic chemistry at the same time. He still collaborates with his undergraduate adviser, professor Phil Crews.

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